Problem: Simplify the following expression: $z = \dfrac{1}{3p} - \dfrac{1}{2p}$
Explanation: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $3p$ and $2p$ $\lcm(3p, 2p) = 6p$ $ z = \dfrac{2}{2} \cdot \dfrac{1}{3p} - \dfrac{3}{3} \cdot \dfrac{1}{2p} $ $z = \dfrac{2}{6p} - \dfrac{3}{6p}$ $z = \dfrac{2 -3}{6p}$ $z = \dfrac{-1}{6p}$